US4450336A - Super-fine finish EDM method and apparatus - Google Patents

Super-fine finish EDM method and apparatus Download PDF

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Publication number
US4450336A
US4450336A US06/288,054 US28805481A US4450336A US 4450336 A US4450336 A US 4450336A US 28805481 A US28805481 A US 28805481A US 4450336 A US4450336 A US 4450336A
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machining
workpiece
switch
electrical
gap
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US06/288,054
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English (en)
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Kiyoshi Inoue
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Inoue Japax Research Inc
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Inoue Japax Research Inc
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23H—WORKING OF METAL BY THE ACTION OF A HIGH CONCENTRATION OF ELECTRIC CURRENT ON A WORKPIECE USING AN ELECTRODE WHICH TAKES THE PLACE OF A TOOL; SUCH WORKING COMBINED WITH OTHER FORMS OF WORKING OF METAL
    • B23H1/00—Electrical discharge machining, i.e. removing metal with a series of rapidly recurring electrical discharges between an electrode and a workpiece in the presence of a fluid dielectric
    • B23H1/02—Electric circuits specially adapted therefor, e.g. power supply, control, preventing short circuits or other abnormal discharges
    • B23H1/022—Electric circuits specially adapted therefor, e.g. power supply, control, preventing short circuits or other abnormal discharges for shaping the discharge pulse train

Definitions

  • the present invention relates to an electrical discharge machining (EDM) method and apparatus for machining a conductive workpiece in which a tool electrode is spacedly juxtaposed with the workpiece to define a machining gap therewith filled with a dielectric liquid and a succession of localized, time-spaced and randomly dispersed machining electrical discharges are effected between the tool electrode and the workpiece across the machining gap to remove stock from the workpiece uniformly over the surface juxtaposed with the tool electrode.
  • EDM electrical discharge machining
  • the EDM process makes use of electroerosive power pulses applied between a workpiece and a tool electrode spacedly juxtaposed across a machining gap filled with a dielectric liquid (e.g. Kerosene or distilled water) which also serves to carry away from the machining gap the detritus of the electrical discharge machining process.
  • a dielectric liquid e.g. Kerosene or distilled water
  • the tool electrode is generally formed with the desired configuration of the cavity or shape complementarily desired in the workpiece.
  • a train of power pulses are then formed to create localized, discrete and randomly dispersed stock removal discharges which produce cumulatively overlapping craters in the workpiece surface; the total surface juxtaposed with the tool electrode is thus machined uniformly over the parts thereof confronting the tool electrode and receives a configuration conforming to the shape of the tool electrode.
  • TW-EDM traveling-wire or wire-cut electrical discharge machining
  • the tool electrode is constituted by a continuous, axially-traveling elongate wire-like electrode and a two- or three-dimensional relative displacement between the wire and the workpiece yields a desired shaped configuration in or on the workpiece.
  • a servo system designed to maintain a predetermined gap spacing substantially constant or to approach the desired gap spacing as accurately as possible.
  • the servo arrangement may also function to respond to gap short-circuiting and arcing conditions to retract the electrode relative to the workpiece thereby removing such conditions.
  • the tool electrode is advanced relatively towards the workpiece by servo feed means adapted to maintain the machining gap spacing substantially constant and thereby to allow stock removal discharges to be successively created.
  • the tool electrode in sinking-type EDM is generally formed with the desired configuration of the cavity or shape complementarily desired in the workpiece. Thus, the total surface eventually juxtaposed with the tool is machined over those portions thereof which confront the tool electrode and receives a configuration conforming to the shape of the tool electrode.
  • a two- or three- dimensional relative displacement is effected between the electrode and the workpiece to yield a desired shaped configuration in or on the workpiece corresponding to the path of the relative displacement.
  • the contamination of the machining gap region with chips, tar and gases produced by machining discharges may be eliminated by continuously or intermittently flushing the gap with a fresh machining fluid and/or intermittently or cyclically retracting the tool electrode away from the workpiece to allow the fresh machining medium to be pumped into the machining gap and the machining contaminants to be carried away from the latter.
  • Parameters of individual and successive electrical discharges or machining current pulses, especially pulse on-time ⁇ on and peak current Ip are, for a given combination of electrode materials and other machining settings, determinative of stock removal characteristics per single pulse delivery and hence of critical machining results, i.e. removal rate, surface roughness and relative electrode wear and, therefore, must be adjusted, in conjunction with pulse off-time, to establish a particular machining condition suitable to yield the desired machining results.
  • These parameters are adjusted individually at pulse source circuitry in the power supply or a pulse generator which is, preferably, of solid-state or semiconductor switching type.
  • the present inventor has observed that in a conventional EDM arrangement, no matter how accurate the setting of these parameters is done at the pulse source in the power supply, the pulse becomes distorted while being generated and transmited to the gap through the gap discharge circuit. It has been observed that the distortion is brought about due to stray capacitances inherently distributed in the gap discharge circuitry, which circuitry includes the machining gap between the tool electrode and the workpiece separated by the dielectric liquid, a semiconductor power switching network for pulsing a DC source, various leads in the power supply, cables connecting the power switch to the gap site, and conductors leading from the power cables for directly energizing the tool electrode and workpiece, and also to some extent environmental circuit units for mechanical arrangements.
  • stray capacitances are present generally across the machining gap between the tool electrode and the workpiece separated by the dielectric liquid, at the interfaces between the emitter and base of a semiconductor element in the switch unit for pulsing a DC power supply to produce the power pulses, and between the parallel conductors in a printed circuit board, lead cables, and at the portions of insulators for the electrode supporting head and for the workpiece support.
  • the stray capacitances have been found to amount to 100 to 1000 picofarads or more in a conventional EDM arrangement using, as a dielectric liquid, kerosene having a specific resistivity of 10 10 to 10 12 ohm-cm for machining a workpiece area in excess of 4 cm 2 .
  • Another object of the invention is to provide an EDM method and apparatus which enable an extremely fine finish to be achieved with an extremely low wear of the tool electrode.
  • Still another object of the invention is to provide an EDM method and apparatus which afford an excellent machined surface quality, better machining performance, an increased removal rate and a reduced tool wear.
  • a method of electrical-discharge-machining an electrically conductive workpiece wherein a tool electrode is spacedly juxtaposed with the workpiece to define a machining gap therewith filled with a dielectric liquid comprises: effecting a succession of localized, time-spaced and repetitive machining electrical discharges between the tool electrode and the workpiece across the machining gap to produce stock removal from the workpiece uniformly over the surface thereof juxtaposed with the tool electrode; and improving the surface finish of the stock-removal surface of the workpiece by discharging electrical charge stored due to a stray capacitance across the tool electrode and the workpiece, through an electrical shunt circuit in parallel with the machining gap immediately prior to initiation of each of the successive machining electrical discharges across the machining gap.
  • the electrical charge is discharged through the gap shunt circuit by turning a shunt switch provided in the gap shunt circuit into conduction.
  • the switch is turned into conduction following termination of the machining electrical discharge immediately preceding each of the machining electrical discharges.
  • the switch is turned into conduction after a predetermined delay time following the termination of the immediately preceding electrical discharge.
  • the switch is held in conduction for a predetermined time duration which should preferably range between 10 and 100 nanoseconds.
  • the said succession of machining electrical discharges are effected by applying successive, time-spaced and repetitive electrical power pulses between the tool electrode and the workpiece across the machining gap.
  • the successive power pulses may be applied across the machining gap by repetitively turning on and off a power switch connected in series with a DC source, the tool electrode and the workpiece.
  • the shunt switch is then turned into nonconduction simultaneously when the power switch is turned on.
  • the shunt switch may be turned into conduction immediately following the turn-off of the power switch but, preferably, after a predetermined delay time following the turn-off of the power switch.
  • the shunt switch is held conducted for a predetermined time duration which should preferably range from 10 to 100 nanoseconds.
  • the invention also provides, in a second aspect thereof, an electrical discharge machining (EDM) apparatus comprising: means for positioning a tool electrode in spaced juxtaposition with a workpiece to define a machining gap therebetween; means for supplying a dielectric liquid into the machining gap, power-supply means for effecting a succession of localized, time-spaced and repetitive machining electrical discharges between the tool electrode and the workpiece across the machining gap to produce stock removal from the workpiece uniformly over the surface thereof juxtaposed with the tool electrode; and means for discharging electrical charge stored due to a stray capacitance across the tool electrode and the workpiece, through an electrical shunt circuit in parallel with the machining gap immediately prior to initiation of each of the machining electrical discharges across the machining gap.
  • EDM electrical discharge machining
  • the means for discharging includes a shunt switch connected in the gap shunt circuit between the tool electrode and the workpiece and control means for turning the shunt switch into conduction to discharge the electrical charge through the gap shunt circuit.
  • the control means is operable for turning the shunt switch into conduction following termination of the machining electrical discharge immediately preceding each of the machining electrical discharges.
  • the control means is preferably operable for turning the shunt switch into conduction after a predetermined delay time following the termination of the immediately preceding machining electrical discharge and is operable for holding the shunt switch in conduction for a predetermined time duration.
  • time-setting means is associated with the control means for setting the time duration in the range between 10 and 100 nanoseconds.
  • the power-supply means may comprise a pulse generator for applying successive, time-spaced and repetitive power pulses across the machining gap, thereby producing the succession of machining electrical discharges between the tool electrode and the workpiece.
  • the pulse generator may comprise a DC source, a power switch connected in series with the DC source, the tool electrode and the workpiece and pulsing means for repetitively turning on and off the power switch to provide the successive power pulses across the machining gap.
  • the control means is then operable for turning the shunt switch into nonconduction substantially simultaneously when the power switch is turned on.
  • the control means may be operable for turning the shunt switch into conduction substantially simultaneously with the turn-off of the power switch.
  • control means is operable for turning the shunt switch into conduction after a predetermined delay time following the turn-off of the power switch which terminates the machining electrical discharge immediately preceding each of the machining electrical discharges.
  • Time-setting means may preferably be associated with the control means for holding the shunt switch in conduction for a predetermined time period which should preferably range from 10 to 100 nanoseconds.
  • the pulse generator may also comprise a DC source, a capacitor connected in parallel with the DC source and the machining gap, a charging switch connected in series with the DC source and the capacitor, and pulsing means for repetitively turning on and off the capacitor-charging switch thereby to permit the capacitor to be repetitively charged by the DC source and the charge on the capacitor to be discharged through the machining gap to provide thereto the successive power pulses.
  • the control means may then be operable for turning the shunt switch into conduction and holding it in conduction immediately prior to the turn-on of the charging switch.
  • the pulse generator may also comprise a DC source, a transformer having a primary winding connected via a power switch to the DC source and a secondary winding, a capacitor in parallel with the secondary winding and the machining gap, a unidirectional current conducting element connected between the secondary winding and the capacitor and pulsing means for repetitively turning on and off the power switch so that the capacitor is charged repetitively by input pulses which develop at the transformer secondary and the repetitive discharging of the charge on the capacitor provides the successive power pulses to the machining gap.
  • the control means may then be operable for turning the shunt switch into conduction in phase with the turn-on of the power switch or alternatively for turning the shunt switch into conduction out of phase with the turn-on or in phase with the turn-off of the power switch to discharge the electrical charge due to the stray capacitance through the gap shunt circuit immediately prior to initiation of each of the machining electrical discharges across the machining gap.
  • FIG. 1 is a waveform diagram schematically illustrating a discharge or machining current pulse which develops across an EDM gap and exhibits a distortion due to stray capacitance commonly present in the gap discharge circuit in an EDM circuit arrangement;
  • FIG. 2 is a circuit diagram schematically illustrating a first embodiment of the present invention
  • FIGS. 3(a) and 3(b) are waveform diagrams illustrating respectively control pulses (A) for producing machining electrical discharges and gap-shunting pulses (B) in the arrangement of FIG. 2;
  • FIG. 4 is a circuit diagram schematically illustrating a second embodiment of the present invention.
  • FIGS. 5(a), 5(b), 5(c), 5(d) and 5(e) are waveform diagrams illustrating various signal pulses (C), (D), (E), (F) and (G) which develop at different portions in the arrangement of FIG. 4; and
  • FIGS. 6 and 7 are circuit diagrams schematically illustrating further embodiments of the present invention.
  • a stray capacitance is generated generally across the EDM gap between the tool electrode and the workpiece separated by a dielectric liquid and also is included at the interfaces between the elements in the gap discharge circuit. It has been observed that the gap stray capacitance amounts to 100 picofarads or more when the dielectric liquid is constituted, say, by kerosene having a specific resistivity of 10 10 to 10 12 ohm-cm and the tool electrode has a machining area in excess of 4 cm 2 . When stray capacitances at the various interfaces of the elements are included, the total value even reaches 1 microfarad or more.
  • the additional currentIp 0 superimposed on the current magnitude Ip to produce the initial peak current Ip 1 and the time ⁇ on1 are expressed as follows:
  • the present invention seeks to provide a novel arrangement whereby the adverse influence of the stray capacitance in the gap discharge circuit onthe surface finish and other machining end result factors is effectively eliminated.
  • FIG. 2 there is shown an EDM circuit arrangement for embodying the present invention whereby the presence of the adverse stray capacitance is effectively circumvented.
  • the arrangement shown includes a conventional EDM power supply 1 comprising a DC source 2 and a power switch 3 connected in series with the DC source 2 and an EDM gap G formed between a tool electrode E and a workpiece W and filled with a dielectric liquid which may, for example, be Kerosene, transformer oil or distilled water and is supplied from a conventional dielectric supply unit (not shown).
  • the tool electrode E is advanced into the workpiece W by a servofeed unit 4 which functions to maintain the machining gap substantially constant.
  • the power switch 3 may as is typically be a bank of transistors and is energized via an amplifier stage 5 by signal pulses furnished by an oscillator 6 and is thereby turned on and off repetitively to provide a sequence of time-spaced and repetitive electrical power pulses across the EDM gap G.
  • a succession of time-spaced, repetitive, localized and randomly dispersed machining electrical discharges are produced between the tool electrode E and the workpiece W across the machining gap G to remove stock from the workpiece W uniformly over the surface thereof juxtaposed with the tool electrode E.
  • the output voltage of the DC source 2 is adjusted to establish the spark-over voltage of each machining electrical discharge at a desired value whereas a variable resistor 7 in the power circuit 1 is adjusted to set up a desired current magnitude Ip of each machining electrical discharge (FIG. 1).
  • the discharge duration oron-time ⁇ on as well as the pulse off-time ⁇ off or time interval between successive machining pulses is basically set up in the signal pulser 6.
  • the pulse generator 1 incorporates a gap shunt circuit 8 connected to the tool electrode E and the workpiece W in parallel with the machining gap G and including a gap shunt switch 9.
  • This switch is shown by a transistor having its emitter and collector and electrodes connected to the series circuit that includesin series the workpieceW, the machining gap G and the tool electrode E and a resistor 10 which represents the circuit resistance of the gap shunt circuit 8.
  • the base electrode of the gap shunt switch 9 is shown to be energizable by a phase-reversing circuit 11 leading from the oscillator 6 which controls the power switch 3.
  • the circuit 11 is thus adapted to respond to successive signals pulses as shown by A in FIG.
  • the modified arrangement shown in FIG. 4 in which the same reference numerals and symbols as in FIG. 2 designate the same components includes asignal source 12 constituted by an oscillator which furnishes signal pulsesof preset on-time, off-time and frequency designated by C in FIG. 5(a).
  • Theoutput of the oscillator 12 is applied to a differentiator circuit 13 and to a phase-reversing circuit 14.
  • the output of the differentiator circuit 13 is shown by D in FIG. 5(b) and is applied to the gap shunt switch 9 anda futher phase-reversing circuit 15 whose output is shown by E in FIG. 5(c).
  • the output of the phase-reversing circuit 15 i.e.
  • pulses E and the output of the phase-reversing circuit 14 shown by pulses F in FIG. 5(d) are combined at an AND gate 16 whose output thus assumes a waveform shown by pulses G in FIG. 5(e).
  • the output of the AND gate 16 or a succession ofsignal pulses G is applied via an amplifier 5 to the power switch 3 to repetitively turn on and off the latter and this provides a succession of electrical power pulses across the EDM gap G, thereby effecting successivemachining electrical discharges between the tool electrode E and the workpiece W to remove stock from the workpiece W from the surface thereof juxtaposed with the tool electrode E. It will be apparent that each D pulse develops at the trailing edge of each C pulse and hence at the leading edge of each G pulse.
  • the gap shunt switch 9 is turned into conduction and held conductive to short-circuit the EDM gap for a shunt time duration ⁇ o (FIG. 5(b) immediately prior to initiation of each machining pulse G.
  • ⁇ o a shunt time duration
  • each D pulse is triggered after a fixed delay time which follows termination of each machining pulse G and which is here equal to the duration ⁇ 1 of signalpulses C.
  • the effective elimination of the added current component Ip 0 or in Ip 1 in FIG. 1 is again in the embodiment of FIG. 4 achieved to render each machining discharge current waveform rectangular with a current magnitude Ip and a pulse duration precisely adjusted at the setting circuits.
  • the pulse generator for applying a succession of time-spaced repetitive power pulses across the machining gap G may also be one as shown in FIG. 6or one as shown in FIG. 7.
  • FIG. 6 the same reference numerals and symbols as in the previous FIGURES are used to refer to the same components.
  • FIG. 6 comprise a DC source 2, a storage capacitor 17 connected in parallel to the DC source 2 and the EDM gap G and a power switch 3 connected in series between the DC source 2 and the capacitor 17.
  • the power switch 3 is turned on and off repetitively with signal pulses furnished from an oscillator 6 to periodically charge the capacitor 17 andto permit the charge stored thereon in each charging cycle to be dischargedthrough the EDM gap to provide a succession of time-spaced repetitive impulses thereat.
  • a one-shot multivibrator 18 is provided responsive to each signal pulse of the oscillator 6 to provide a short-duration pulse of a duration of 10 to 100 nanoseconds and thereby torender the gap shunt switch 9 conductive.
  • the switch 9 is turned into conduction and held conductive for the short time period of this duration which occurs at the leading edge of each signal pulse of the oscillator 6.
  • the charge on the storage capacitor 17 is discharged through the machining gap G.
  • the discharging of the capacitor 17 terminates at an instant prior to the turn-on of the power switch 3 or before a signal pulse from the oscillator builds up. When this signal pulse occurs, the capacitor 17 commences charging thereon.
  • FIG. 7 comprises a variable-output DC source 2, a transformer 19 having a primary winding 19a connected in series with the DC source 2 via a power switch 3 and a secondary winding 19b, a storage capacitor 17 connected in parallel with the secondary winding 19b of the transformer 19 and the EDM gap G and a unidirectional current conducting element or diode 20 connected in series between the secondary winding 19b and the storage capacitor 17.
  • the power switch 3 is repetitively turned onand off with a succession of signal pulses furnished from an oscillator 6 to apply a succession of output pulses to the primary winding 19a of the transformer 19. The latter then develops at its secondary winding 19b transformed bi-directional output pulses which are rectified by the diode 20 into a succession of unidirectional pulses.
  • the storage capacitor 17 isperiodically charged with the latter pulses and the charge stored on the capacitor 17 in each charging cycle is discharged through the EDM gap G toprovide a succession of time-spaced and recurrent impulses thereat.
  • the charging pulses each of which is synchronous with the trailing edge of each signal pulse from the oscillator are applied to the storage capacitor 17.
  • the gap shunt switch 9 may be turned into conduction and held conductive for the duration of each signal pulse from the oscillator 6.
  • the discharging of the capacitor 17 terminates prior to the turn-on of the power switch 3 or before each signal pulse of the oscillator 6 develops.
  • the capacitor 17 commences charging in response to the corresponding output pulse which develops at the secondary winding 19b of the transformer 19. It will thus be apparent that the gap shunt switch 9 is held conductive to short-circuit the machining gap G through the gap shunt circuit 8 after a delay time following the termination of each discharging of the storage capacitor 17 or each machining pulse and prior to initiation of each charging of the capacitor 17 and hence immediately prior to initiation of each machining pulse.
  • a phase-reversing circuit 11 may be provided between the oscillator 6 and the gap shunt switch 9.
  • the gap shunt switch 9 is turned into conduction and held conductive for the duration of the time interval between successive signal pulses of the oscillator 6. In each cycle, the discharging of the capacitor 17 terminates prior to the turn-on of the gapshunt switch 9.
  • the gap shunt switch 9 is turned on and held conductive to short-circuit the machining gap G through the gap shuntcircuit 8 after a delay time following the termination of each discharging of the storage capacitor 17 or each machining pulse and prior to initiation of each charging of the capacitor 17 and hence immediately prior to initiation of each machining pulse.
  • the present invention effectively circumvents the adverse effect of the stray capacitance in the gap discharge circuit.
  • the method of the invention is extremely advantageous for EDM operation ina fine and ultra-fine finishing range utilizing machining pulses of an on-time or pulse duration of 0.1 to 10 microseconds.
  • machining pulses of an on-time or pulse duration of 0.1 to 10 microseconds.
  • E/W relative electrode wear

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Electrical Discharge Machining, Electrochemical Machining, And Combined Machining (AREA)
US06/288,054 1980-08-05 1981-07-29 Super-fine finish EDM method and apparatus Expired - Lifetime US4450336A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP55-107395 1980-08-05
JP10739580A JPS5733926A (en) 1980-08-05 1980-08-05 Electric discharge machining device

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US (1) US4450336A (lv)
JP (1) JPS5733926A (lv)
DE (1) DE3131037A1 (lv)
FR (1) FR2488175B1 (lv)
GB (1) GB2081633B (lv)
IT (1) IT1142958B (lv)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4820895A (en) * 1983-12-23 1989-04-11 Fanuc Ltd. Electric discharge machine position finding apparatus
US20130168362A1 (en) * 2011-12-30 2013-07-04 Agie Charmilles Sa Electric discharge machining method and apparatus
US20170266744A1 (en) * 2015-10-30 2017-09-21 Mitsubishi Electric Corporation Wire electric discharge machine, control method of control device of wire electric discharge machine, and positioning method
US20190260415A1 (en) * 2017-06-02 2019-08-22 Psemi Corporation Method and Apparatus for Switching of Shunt and Through Switches of a Transceiver

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS63174816A (ja) * 1987-01-16 1988-07-19 Hoden Seimitsu Kako Kenkyusho Ltd 放電加工機用電源装置
JP2749656B2 (ja) * 1989-08-16 1998-05-13 株式会社放電精密加工研究所 放電加工用電源回路
JP2914104B2 (ja) * 1993-06-30 1999-06-28 三菱電機株式会社 放電加工方法及びその装置、並びにこの放電加工装置に適用可能な、静電容量可変装置及びインダクタンス可変装置

Citations (7)

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US3056065A (en) * 1959-06-23 1962-09-25 Elox Corp Michigan Spark machining methods and apparatus
US3109120A (en) * 1960-10-20 1963-10-29 Gen Motors Corp Electrical stock removal apparatus
GB1168610A (en) * 1965-10-16 1969-10-29 Philips Electronic Associated Spark Erosion Method and Apparatus.
US3956609A (en) * 1973-08-31 1976-05-11 Ateliers Des Charmilles S.A. Pulse generator for electro-erosion machining apparatus
US4162425A (en) * 1977-06-30 1979-07-24 Detector Electronics Corporation Ultraviolet detection tube quenching circuitry
US4237370A (en) * 1977-06-03 1980-12-02 Elmapa N.V. Pulse generator for metal machining by electric discharges
US4335294A (en) * 1979-07-25 1982-06-15 Inoue-Japax Research Incorporated EDM Method and apparatus having a gap discharge circuit constructed with limited stray capacitances

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3056065A (en) * 1959-06-23 1962-09-25 Elox Corp Michigan Spark machining methods and apparatus
US3109120A (en) * 1960-10-20 1963-10-29 Gen Motors Corp Electrical stock removal apparatus
GB1168610A (en) * 1965-10-16 1969-10-29 Philips Electronic Associated Spark Erosion Method and Apparatus.
US3956609A (en) * 1973-08-31 1976-05-11 Ateliers Des Charmilles S.A. Pulse generator for electro-erosion machining apparatus
US4237370A (en) * 1977-06-03 1980-12-02 Elmapa N.V. Pulse generator for metal machining by electric discharges
US4162425A (en) * 1977-06-30 1979-07-24 Detector Electronics Corporation Ultraviolet detection tube quenching circuitry
US4335294A (en) * 1979-07-25 1982-06-15 Inoue-Japax Research Incorporated EDM Method and apparatus having a gap discharge circuit constructed with limited stray capacitances

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4820895A (en) * 1983-12-23 1989-04-11 Fanuc Ltd. Electric discharge machine position finding apparatus
US20130168362A1 (en) * 2011-12-30 2013-07-04 Agie Charmilles Sa Electric discharge machining method and apparatus
US20170266744A1 (en) * 2015-10-30 2017-09-21 Mitsubishi Electric Corporation Wire electric discharge machine, control method of control device of wire electric discharge machine, and positioning method
US20190260415A1 (en) * 2017-06-02 2019-08-22 Psemi Corporation Method and Apparatus for Switching of Shunt and Through Switches of a Transceiver
US10686484B2 (en) * 2017-06-02 2020-06-16 Psemi Corporation Method and apparatus for switching of shunt and through switches of a transceiver
US11070243B2 (en) * 2017-06-02 2021-07-20 Psemi Corporation Method and apparatus for switching of shunt and through switches of a transceiver

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Publication number Publication date
GB2081633B (en) 1984-01-18
JPS5733926A (en) 1982-02-24
IT8149047A0 (it) 1981-08-04
GB2081633A (en) 1982-02-24
DE3131037C2 (lv) 1988-10-20
DE3131037A1 (de) 1982-04-01
FR2488175B1 (fr) 1985-11-15
FR2488175A1 (fr) 1982-02-12
IT1142958B (it) 1986-10-15

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